To follow Part 1, Part 2 and Part 3 about the System Event on Tasmania on Friday 14th October 2022 we’ve been tinkering away in the background with some additional data about the event – both from the AEMO and from others.
Because this is being done in ‘spare’ time, it might be any articles to follow-on might be brief, such as with this zoomed in view of the 4 x system frequency traces over a 7 minute period focused on the initial period of the event:
With respect to the above:
1) Clearly the TAS frequency separates from the mainland
2) But TAS NORTH and TAS SOUTH are also slightly different (one lags the other – due to timing of SCADA snaps?)
3) And the mainland frequency lifted a little after TAS separated, losing the ~400MW or so of exports being sent that way and buoying the frequency in the mainland.
Will look forward to reading the upcoming AEMO interim report on the event.
The different frequency for north vs. south Tasmania may reflect an oscillation between the 2 generation blocks especially if the lost circuits reulted in a higher impedance link between the 2 areas as well as different inertias and governor responses.
The frequency in Tasmania is always separated from the mainland because there’s only a DC link, it’s not synchronised to the rest of the NEM.
My comment about a possible frequency oscillation within Tasmania assumes that BassLink was still out of service given that it tripped during the initial fault disturbance. Another possibilty is the timing of any automatic reclose of the 2 faulted transmission lines.